Transparent electronics is today one of the most advanced topics for a wide range of device applications. The key components are wide bandgap semiconductors, where oxides of different origins play an important role, not only as passive component but also as active component, similar to what is observed in conventional semiconductors like silicon. Transparent electronics has gained special attention during the last few years and is today established as one of the most promising technologies for leading the next generation of flat panel display due to its excellent electronic performance. In this paper the recent progress in n- and p-type oxide based thin-film transistors (TFT) is reviewed, with special emphasis on solution-processed and p-type, and the major milestones already achieved with this emerging and very promising technology are summarizeed. After a short introduction where the main advantages of these semiconductors are presented, as well as the industry expectations, the beautiful history of TFTs is revisited, including the main landmarks in the last 80 years, finishing by referring to some papers that have played an important role in shaping transparent electronics. Then, an overview is presented of state of the art n-type TFTs processed by physical vapour deposition methods, and finally one of the most exciting, promising, and low cost but powerful technologies is discussed: solution-processed oxide TFTs. Moreover, a more detailed focus analysis will be given concerning p-type oxide TFTs, mainly centred on two of the most promising semiconductor candidates: copper oxide and tin oxide. The most recent data related to the production of complementary metal oxide semiconductor (CMOS) devices based on n- and p-type oxide TFT is also be presented. The last topic of this review is devoted to some emerging applications, finalizing with the main conclusions. Related work that originated at CENIMAT|I3N during the last six years is included in more detail, which has led to the fabrication of high performance n- and p-type oxide transistors as well as the fabrication of CMOS devices with and on paper.

Oxide Semiconductor Thin‐Film Transistors: A Review of Recent Advances

https://iopscience.iop.org/article/10.1088/1468-6996/11/4/044305/pdf

Present status of amorphous In–Ga–Zn–O thin-film transistors

An object of the present invention is to decrease the resistance of a power supply line, to suppress a voltage drop in the power supply line, and to prevent defective display. A connection terminal portion includes a plurality of connection terminals. The plurality of connection terminals is provided with a plurality of connection pads which is part of the connection terminal. The plurality of connection pads includes a first connection pad and a second connection pad having a line width different from that of the first connection pad. Pitches between the plurality of connection pads are equal to each other.

Semiconductor device and display device

To provide a semiconductor device and a display device which can be manufactured through a simplified process and the manufacturing technique. Another object is to provide a technique by which a pattern of wirings or the like which is partially constitutes a semiconductor device or a display device can be formed with a desired shape with controllability.

Semiconductor device, electronic device, and method of manufacturing semiconductor device

With the arising of global climate change and resource shortage, in recent years, increased attention has been paid to environmentally friendly materials. Trees are sustainable and renewable materials, which give us shelter and oxygen and remove carbon dioxide from the atmosphere. Trees are a primary resource that human society depends upon every day, for example, homes, heating, furniture, and aircraft. Wood from trees gives us paper, cardboard, and medical supplies, thus impacting our homes, school, work, and play. All of the above-mentioned applications have been well developed over the past thousands of years. However, trees and wood have much more to offer us as advanced materials, impacting emerging high-tech fields, such as bioengineering, flexible electronics, and clean energy. Wood naturally has a hierarchical structure, composed of well-oriented microfibers and tracheids for water, ion, and oxygen transportation during metabolism. At higher magnification, the walls of fiber cells have an interes...

https://www.fpl.fs.fed.us/documnts/pdf2016/fpl_2016_zhu001.pdf

Wood-Derived Materials for Green Electronics, Biological Devices, and Energy Applications.

A thin-film device includes a first electrical insulator, an oxide-semiconductor film formed on the first electrical insulator, and a second electrical insulator formed on the oxide-semiconductor film, the oxide-semiconductor film defining an active layer. The oxide-semiconductor film is comprised of a first interface layer located at an interface with the first electrical insulating insulator, a second interface layer located at an interface with the second electrical insulator, and a bulk layer other than the first and second interface layers. A density of oxygen holes in at least one of the first and second interlayer layers is smaller than a density of oxygen holes in the bulk layer.

Thin-film device and method of fabricating the same

Eco-friendly and low-cost cellulose nanofiber paper (nanopaper) is a promising candidate as a novel substrate for flexible electron device applications. Here, a thin transparent nanopaper-based high-mobility organic thin-film transistor (OTFT) array is demonstrated for the first time. Nanopaper made from only native wood cellulose nanofibers has excellent thermal stability (>180 °C) and chemical durability, and a low coefficient of thermal expansion (CTE: 5–10 ppm K-1). These features make it possible to build an OTFT array on nanopaper using a similar process to that for an array on conventional glass. A short-channel bottom-contact OTFT is successfully fabricated on the nanopaper by a lithographic and solution-based process. Owing to the smoothness of the cast-coated nanopaper surface, a solution processed organic semiconductor film on the nanopaper comprises large crystalline domains with a size of approximately 50–100 μm, and the corresponding TFT exhibits a high hole mobility of up to 1 cm2V-1 s-1 and a small hysteresis of below 0.1 V under ambient conditions. The nanopaper-based OTFT also had excellent flexibility and can be formed into an arbitrary shape. These combined technologies of low-cost and eco-friendly paper substrates and solution-based organic TFTs are promising for use in future flexible electronics application such as flexible displays and sensors.

Transparent Nanopaper-Based Flexible Organic Thin-Film Transistor Array

The transfer characteristics of amorphous InGaZnO4 thin-film transistors (a-IGZO TFTs) were measured at temperatures ranging from 298 to 523 K in order to analyze the behavior of the above-threshold (ON state) and subthreshold regions. For comparison, the transfer characteristics of a hydrogenated amorphous silicon TFT (a-Si:H TFT) were measured in the same temperature range. We developed a simple analytical model that relates the threshold voltage (Vt) decrease due to increasing temperature to the formation of point defects in a-IGZO. It is well known that the formation of point defects results in the generation of free carriers in oxide semiconductors. Incorporating the analytical model with the experimental transfer characteristics data taken at high temperatures over 423 K, we estimated the formation energy to be approximately 1.05 eV. The Vt decrease because of the generation of point defects is peculiar to a-IGZO TFTs, which is not observed in a-Si:H TFTs. The results for the ON-current activation energy suggested that the density of tail states for a-IGZO is much lower than that for a-Si:H.

https://iopscience.iop.org/article/10.1143/JJAP.48.011301/pdf

Temperature-Dependent Transfer Characteristics of Amorphous InGaZnO4 Thin-Film Transistors

We discuss the ultraviolet (UV) photo-field effects in amorphous InGaZnO4 thin-film transistors (a-IGZO TFTs) compared with those in hydrogenated amorphous silicon (a-Si:H) TFTs. It is shown that the UV illumination induces a much more significant threshold voltage (Vt) decrease and OFF-current increase for the a-IGZO TFTs than for the a-Si:H TFTs. The significant Vt decrease is found to take several tens of min to return to the initial state after switching off the UV light. A qualitative model is introduced to explain the photoresponse unique to the a-IGZO TFTs.

https://iopscience.iop.org/article/10.1143/JJAP.48.010203/pdf

Comparison of Ultraviolet Photo-Field Effects between Hydrogenated Amorphous Silicon and Amorphous InGaZnO4 Thin-Film Transistors

We compare the mutual interactions between the top-and bottom-gate fields in a dual-gate structure for amorphous InGaZnO4 (a-IGZO) and hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs). We find that a-IGZO TFTs show more significant mutual interactions than a-Si:H TFTs. By using a wide variety of a-IGZO TFTs with varying thicknesses of a-IGZO and gate-insulator layers, we have investigated, on the basis of a conventional fully depleted n-channel silicon-on-insulator model, the mechanism behind parallel shifts in transfer characteristics caused by negative top-gate voltages. Experimental results, even for relatively thick (over 150 nm) a-IGZO layers, are in good agreement with the fully depleted model. This fact may be related to the nonexistence of hole accumulation in a-IGZO, which is an intrinsic property of oxide semiconductors. In contrast, for the a-Si:H TFTs, there is a considerable discrepancy between the experimental results and the model. This discrepancy probably results from the limited penetration of band bending into the a-Si:H layer, as well as from the hole accumulation at the top interface. Such analysis of a-IGZO TFTs is of practical importance in device applications because many issues related to the fabrication and structure of a-IGZO TFTs may be resolved with a better understanding of dual-gate performance.

Dual-Gate Characteristics of Amorphous $ \hbox{InGaZnO}_{4}$ Thin-Film Transistors as Compared to Those of Hydrogenated Amorphous Silicon Thin-Film Transistors

Mitsuru Nakata

Papers

Thin-film device and method of fabricating the same

Transparent Nanopaper-Based Flexible Organic Thin-Film Transistor Array

Temperature-Dependent Transfer Characteristics of Amorphous InGaZnO4 Thin-Film Transistors

Comparison of Ultraviolet Photo-Field Effects between Hydrogenated Amorphous Silicon and Amorphous InGaZnO4 Thin-Film Transistors

Dual-Gate Characteristics of Amorphous $ \hbox{InGaZnO}_{4}$ Thin-Film Transistors as Compared to Those of Hydrogenated Amorphous Silicon Thin-Film Transistors